Magnet structure and magnet support structure in an electromagnetically operated switch

ABSTRACT

A MULTIPLE CONTACT ELECTROMAGNETICALLY OPERATED SWITCH HAVING A HOUSING THAT PROVIDES AN ENCLOSURE FOR THE ELECTROMAGNET OPERATOR OF THE SWITCH. THE HOUSING INCLUDES AT LEAST ONE METAL PART THAT HAS A HIGH COEFFICIENT OF THERMAL CONDUCTIVITY SO THE HOUSING ACTS AS A HEAT SINK AND A RADIATOR FOR HEAT GENERATED WITHIN THE ELECTROMAGNET WHEN A MAGNET COIL OF THE ELECTROMAGNET IS ENERGIZED. THE HEAT SINKING CAPABILITY IS ACCOMPLISHED BY RESILIENTLY SUPPORTING A PORTION OF A MAGNET CORE FOR THE ELECTRO-   MAGNET ON THE METAL HOUSING PART IN A MANNER WHICH WILL PERMIT THE MAGNET CORE TO MOVE TOWARD THE ARMATURE PORTION OF THE ELECTROMAGNET WHILE THE ARMATURE IS MOVING TOWARD THE MAGNET CORE TO REDUCE THE IMPACT SHOCK WHICH OCCURS WHEN THE ARMATURE ENGAGE THE MAGNET CORE.

Jan. 5,1971 E wHlTlNG ET AL 3,553,614

MAGNET STRUCTURE AND MAGNET SUPPORT STRUCTURE IN AN ELECTROMAGNETICALLY OPERATED SWITCH Filed July 23. 1969 2 Sheets-Sheet 1 MERLIN Y. TURNBULL Jan. 5, 1971 w rn ET AL 3,553,614

MAGNET STRUCTURE AND MAGNET SUPPORT STRUCTURE IN AN ELECTROMAGNETICALLYY OPERATED SWITCH 2 Sheets-Sheet 2 Filed July 25. 1969 u G R W WH V H R TJWU W T N Y I D ma AE H M United States Patent 3 553 614 MAGNET STRUCTURE AND MAGNET SUPPORT STRUCTURE IN AN ELECTROMAGNETICALLY OPERATED SWITCH Harold E. Whiting, Milwaukee, and Merlin Y. Tumbull, Brooktield, Wis., assignors to Square D Company, Park Ridge, Ill., a corporation of Michigan Filed July 23, 1969, Ser. No. 844,029 Int. Cl. H01h 50/16 US. Cl. 335132 ABSTRACT OF THE DISCLOSURE A multiple contact electromagnetically operated switch having a housing that provides an enclosure for the electromagnet operator of the switch. The housing includes at least one metal part that has a high coefiicient of thermal conductivity so the housing acts as a heat sink and a radiator for heat generated within the electromagnet when a magnet coil of the electromagnet is energized. The heat sinking capability is accomplished by resiliently supporting a portion of a magnet core for the electromagnet on the metal housing part in a manner which will permit the magnet core to move toward the armature portion of the electromagnet while the armature is moving toward the magnet core to reduce the impact shock which occurs when the armature engages the magnet core.

The present invention relates to electromagnetic type switching devices and more particularly to the constructional details and the arrangement of the components of a multiple contact electromagnetically operated switching device.

Electromagnetic switching devices of the type with which the present invention is concerned are commonly known as contactors and are furnished as devices of varying sizes having ratings in accordance with standards promulgated by the National Electrical Manufacturers Association, commonly known as NEMA. An example of a contactor construction which is particularly suited to control loads of 50 amperes or less, which corresponds to a NEMA Size 2 device, is disclosed in US. Pat. No. 3,354,415, which was granted on Nov. 21, 1967, to the inventors Joseph I. Gribble, Kenneth J. Marien and Harold E. Whiting.

While the proportions of the device shown in the Gribble et al. patent may be increased to control currents greater than 50 amperes, economic and physical size limitations dictate that additional features should be incorporated therein if currents having a magnitude two or three times 50 amperes are to be controlled by the device. The structure according to the present invention provides increased pressures between the switching contacts and a greater contact mass to enable the device to conduct the higher current values without overheating and without increasing the contact bounce characteristics of the device than was included in the structure dis closed in the Gribble et al. patent. Thus while the device according to the present invention incorporates the desirable features and advantages included in the device as disclosed in the Gribble et al. patent, it additionally includes a novel arrangement for supporting the magnet core portion of the electromagnet which will cause the heat Claims generated within the electromagnet to be more readily dissipated and an arrangement that will reduce the impact shock between the armature and the magnet core when the pole faces of the armature and magnet core engage each other.

It is an object of the present invention to provide an electromagnetically operated switch with a magnet support structure which will reduce the shock accompanying the engagement between the armature and magnet core and provide heat sink for conducting heat away from the electromagnet during intervals the electromagnet is energized.

Another object is to resiliently support a magnet core of an electromagnet on a wall of a metal part of a housing so the part will act as a heat sink and aid in dissipating the heat generated within the electromagnet when the electromagnet is energized and permit the magnet core to move toward the armature when the electromagnet is initially energized to reduce the impact shock which is generated by the engagement between the pole faces of the armature and the magnet core.

A further object is to provide an electromagnetically operated switch with a housing that has one metal part formed of a material that has a high coefiicient of thermal conductivity and forms the external walls and the internal walls of a cavity within the housing and to position an electromagnet within the cavity so that the armature portion of the electromagnet is constantly urged by a yieldable force including gravity and a force provided by springs operating on a movable contact carrier to one position in the housing and to resiliently support a portion of a magnet core of the electromagnet on one of the internal metal walls of the housing so the heat generated within the electromagnet during periods when the coil of the electromagnet is energized will be dissipated by the metal housing part and to arrange the resilient supports for the magnet coil so the magnet core moves toward the armature during the interval the armature is moving toward the magnet core when the coil is initially energized.

Further objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawings illustrating certain preferred embodiments in which:

FIG. 1 is a side view partly in section of a de-energized electric switch incorporating an electromagnet structure and support therefor according to the present invention.

FIG. 2 is an end view partly in section of the switch in FIG. 1 taken in the direction of arrows 2-2 in FIG. 1.

FIG. 3 is a top view of the switch in FIG. 1 with a cover removed and the electromagnet energized.

FIG. 4 is an exploded view showing in perspective the components of an electromagnet as used in the switch shown in FIG. 1.

FIG. 5 is an exploded view showing in perspective the components of a resilient support for the magnet core in FIG. 1.

Referring to the drawing, and particularly to FIG. 1, there is shown an electromagnetic switch assembly 20 having a plurality of components that are stacked one upon the other. The components of the assembly include a metal mounting plate 22, an insulating sheet-like member 24, an insulating base 26, an insulation barrier 28, a metal housing 30, and a cover 32, each of which is disclosed and described in an application for US. patent, Ser. No. 844,148, which was filed concurrently herewith.

The metal mounting plate 22 is formed of a stamped metal part and provides a means to secure the switch assembly 20 to a vertical panel and the like, not shown. When the plate 22 is secured to a panel, an edge 34 becomes a bottom edge of the plate 22 and a surface 36 the front surface of the plate 22. The plate 22 has a pair of rearwardly extending indentations 38 along its bottom edge 34 providing a pair of spaced mounting feet having openings 39 therein. The plate 22 also has an indentation 40 extending across its top edge which provides an elongated mounting foot having an opening 41 therein. The mounting feet 38 and 40 with the openings therein are provided for the purpose of securing the plate 22 to a vertical panel. The plate 22 also includes an indentation 42 which extends from the bottom edge 34 rearwardly in the front surface 36 to the indentation 40. The indentation 42 is provided to permit passage of control wires, not shown, from the upper to the lower ends of the switch 20 in the space provided by the indentation. The control wires may be connected in circuit with the switching contacts of a device known as an overload relay, in a manner well known to those skilled in the art. The plate 22 also is provided with suitably located threaded openings which act as mounting holes which are used to secure the insulating sheet-like member 24 and base 26- to the plate 22.

The sheet 24 is preferably formed as a molded insulating part having a relatively thin cross section having a fiat rear surface engaging the front surface 36 to cover a central portion of the indentation 42 so as to act as a cover for the wire trough. The sheet 24 is provided with a pair of circular ribs 44 which are raised on the front surface of the sheet 24 on opposite sides of a vertical center of the plate 22. The ribs 44 act as spring seats as will be later described. The sheet 24 also is provided with portions 46 which are formed along the top and bottom edges of the sheet 24 in alignment with the indentation 42. The portions 46 act as scoops and aid in directing the wires in the portion of the wire trough disposed between the sheet 24 and the plate 22.

As disclosed in the application for U.S. patent, Ser. No. 844,148, supra, the base 26 and the barrier 28 are formed of a molded insulating material having arc suppressing capabilities and cooperate with each other to provide a cavity which is divided into three compartments 48 having equal widths. The base 26 has a rear surface 50 positioned on the insulating sheet 24 and the plate 22 in a secured position by suitable screws which pass through openings in the base 26 and the sheet 24 and are threadedly received in the housing holes in the plate 22. Extending into the material of the base 26 forwardly of the rear surface 50 and through the side walls of the base 26 is a slot 52. The slot 52 is centered on a centerline equidistant between a top wall 54 and a bottom wall 56 of the base 26 and is exposed to each of the compartments 48 by an opening. The compartments 48 each extend between the top wall 54 and the bottom wall 56 and each have a pair of terminal and stationary contact assemblies secured therein.

The terminal and stationary contact assemblies in each of the compartments 48 are arranged so that the contact assemblies of each pair are spaced equidistantly on opposite sides of the slot 52 and face in opposite directions. Each of the contact assemblies includes a terminal member 58 and a contact member 60. When the pairs of terminal and contact assemblies are secured at the opposite ends of the compartments 48, the terminal members 58 will have a wire connecting portion 62 extending external of the top wall 54 and the bottom wall 56 and the contact members 60 will have an inclined stationary contact surface 64 positioned on opposite sides of the slot 52.

As disclosed in an application for US. patent, Ser. No. 844,148, the barrier 28, the metal housing 30 and cover 32 define an internal closed cavity 66 wherein an electromagnet 68 is included. The electromagnet 68 operates a bell crank lever 70 which has a pair of arms 72 connected to a movable U-shaped contact carrier 74 that has a bight portion indicated by the numeral 76 in the drawings. The bight portion 76 is movable forwardly and rearwardly in the slot 52. The movable contact carrier 74 including the bight portion 76 is most clearly disclosed in an application for US. patent, Ser. No. 844,100, concurrently filed herewith which has been assigned by the inventors Merlin Y. Turnbull and Harold E. Whiting to the assignee of the present invention. The barrier 28 has a body portion 78 which provides a front wall for the compartments 48 and suitable ribs, not shown, which provide side walls for the compartments. Extending from the body portion 78 are ears 80 that are arranged to seat upon the forward ends of a pair of posts 82 at the top and bottom walls 54 and 56. The posts 82 each have a threaded insert molded therein and each of the cars 80 has an opening therein which permits the barrier 28 to be removably secured to the front surface of the base 26 by screws 84 which pass through the openings in the ears 80 into the threaded inserts in the posts 82. It is readily apparent that the removal of the screws 84 will permit the assembly including the barrier 28, the housing 30 and the cover 32 to be detached from the base 26 to permit access to the stationary and the movable contacts within the compartments 48 in event the contacts require inspection or replacement.

The movable contact carrier 74 which is partly shown in FIG. 2 is preferably formed as a U-shaped molded part that includes the bight portion 76. The bight portion 76 is received in the slot 52 while arms, 86, which extend from opposite ends of the bight portion 76, extend ex ternally of the side walls of the base 26, have free ends received in channels 88 in the housing 30 defined by portions 90 on the housing 30. The free ends of the arms 86 each receive a bearing 75 on a terminal end on an arm 72 of the bell crank lever 70. Extending forwardly of the bight portion 76 are a plurality of spaced projections 92 each of which extends into one of the compartments 48. The bight portion 76 has a rear surface 94 and each of the projections 92 has a front surface whereon a movable contact member 96 is positioned, in a manner disclosed in an application for US. patent, Ser. No. 844,151, which has been filed by the inventor Merlin Y. Turnbull concurrently herewith.

The housing 30 preferably is formed as a cast metal part which has a high thermal conductivity. While aluminum may be used to form the housing 30, in that it possesses high thermal conductivity and is light weight, because of its resistance to impact the housing part 30 is preferably formed of a zinc die cast material to have a bottom wall 108, a top wall and a pair of side walls 112 and 114 which have a rear edge 115 resting on a front surface 98 of the barrier 28 and an open front wall 116 which is closed by the cover 32. The front surface 98 and the walls 108, 110, 112, and 114 define the cavity 66 which has a front side closed by the cover 32. The cover, when removed, provides access to the electromagnet 68 that is positioned within the cavity 66 for inspection and for service purposes. Extending inwardly from the top wall 110 is a ledge 118 that has a pair of openings therein. Similarly, as shown in FIGS. 1 and 3, extending inwardly from the bottom wall 108 at the intersections of the side walls 112 and 114 are ledges 120 and 122 each having an opening therein. The ledges 118, 120 and 122 are arranged to engage portions of the front surface 98 while the openings therein provide a passage for screws 124 which are threaded into suitably located threaded inserts that are embedded in the barrier 28 to secure the housing 30 to the barrier 28. Additionally extending inwardly along the rear edge 115 from the top wall 110 at the intersection of the side walls 112 and 114 are ledges 126 and 128, each of which has a rear surface resting on the front surface 98 and a front surface 130 wherein spring biased supports 132 and 134 are secured. The spring biased supports are identical, and as shown in FIG. 5, each includes a support 136, a slider 138 and a spring 140. The support 136 has a base portion 142 secured to the front surface of the ledges 126 or 128 and a pair of upstanding walls 144 and 146 extending from the base portion 142. The wall 144 is positioned adjacent an abutment 148 formed on the front surface 98. The wall 144 has a bore 150 extending therethrough. The wall 146 has a dove-tail type slot 152 therein. The slider 138 has a portion 154 shaped to be slidingly received in the slot 152 and a projection 156 extending toward the wall 144 which positions the spring 140 which has one end resting against the wall 144 and its opposite end resting on the portion 154. The projection 156 extends into the bore 150 when the slider, 138, and the spring 140 are assembled with the support 136. The portion 154 has an abutment surface 158 on an end of the portion 154 opposite the projection 156 and a projection 160 extending from the abutment surface 158. The portion 154 is provided with a rounded edge 162 extending at the intersection of the abutment surface 158 and the surface on the portion 1.54 facing the cavity 66. The projection 160 is provided to space the abutment surface 158 slightly from the top wall 110 when the spring biased supports 132 and 134 are secured to the housing 30 with the springs 140 constantly urging the abutment surface 158 toward the top wall 110. As shown in FIGS. 1 and 2, secured to a rear surface 164 of the cover are a pair of spring biased supports 167 and 169 which are identical to the spring biased supports 132 and 134. The electromagnet 68 which is positioned within the cavity 66 includes a magnet coil 100, an armature 102 and a magnet core 166. The magnet coil 100 is positioned by portions of the cover 32 and the surface 98 so that a rectangularly shaped opening 168 through the coil 100 extends along an axis perpendicular to the top and the bottom walls 110 and 108. The armature 102 includes a laminated stack 170 of T-shaped laminated magnet iron pieces and a member 172. The member 172 has a pair of arm portions 174 and 176 secured on opposite sides of the laminated stack 170 by rivets 178 which secure the laminated stack 170 and the arms 174 and 176 together and a portion 180 which interconnects the arm portions 174 and 176. The portion 180 is generally U-shaped and box-like and includes an inner wall 182 that is spaced from and faces upward toward a downward facing wall 184 of the laminated stack 170. An opening 186 is formed in portions of the wall 182 and the arm 176. The opening 186 is sized so an end portion of an operating arm 188 on the bell crank lever 70 may extend into the space between the walls 182 and 184. The arm portion 188 carries a bearing member 190 which is positioned between the walls 182 and 184 and is more clearly described in the application for US. patent, Ser. No. 844,100, supra. When the armature 102 is positioned within the cavity 66, the bearing member 190 will be positioned between the walls 182 and 184 while the stem portion 192 of the armature is received in and partly extends into the opening 168 of the coil 100 and presents a pair of pole faces 194 that face the top wall 110. The magnet core 166 includes a laminated stack of E-shaped laminated magnet iron pieces designated by a numeral 196 and a pair of members 198 and 200. The members 198 and 200 are secured on opposite sides of the laminated stack 196 by rivets 202 which secure the laminations of the stack 196 and the members 198 and 200 together. The laminated stack has an upper wall 204, a pair 8 of pole faces 206 facing downwardly on the outer legs of the E-shaped pieces and a downwardly facing pole face 208.on the end of the center leg of the E-shaped parts. The upper wall 204 is substantially flat and extends substantially over the entire upper end of the E-shaped stack of laminated pieces. The members 198 and 200 each have a pair of identical ears 210 formed thereon. Each of the ears 210 extends perpendicular to the outer face of the main body portion 211 of the respective members 198 and 200 so as to present a surface 212 that is displaced a slight distance downwardly of the upper wall 204 and a surface 214 that faces in the same direction as the pole faces 206 and 208. Further, each of the ears 210 is provided with a notch 216 that extends from a free end 218 of the ear toward the main body portion 211. The switch assembly also includes a pair of springs 220 which are positioned by the ribs 44 and engage the bight portion 76 to constantly urge the movable contact carrier 74 forwardly in the slot 52, a spring 222 which is compressed as the movable contact 96 engages the stationary contacts surfaces 64, terminals 224 for the coil 100 which are accessible through an opening in the cover 32, ledges 226 suitably located in the channels 88 which provide threaded openings for screws which are used to attach the cover 32 to the housing 30 and shading coils 228 adjacent the pole faces 206.

The mounting plate 22, the insulating member 24, the base 26, the stationary contacts assemblies, the movable contact carrier 74 with the movable contacts 96 thereon, the barrier 28, the housing 30 and the bell crank lever which is positioned within the cavity 66 are all assembled in a manner disclosed in the application for US. patent, Ser. No. 844,100, supra. After the foregoing mentioned parts are assembled, the electromagnet 68 is installed in the cavity 66 by assembling the armature 102, coil and the magnet core 166 so that the stem 192 extends into the opening 168 from one side of the coil 100 and the central arm of the E-shaped magnetic core 166 extends into the opening 168 from the other end of the coil 100. The electromagnet 68 is then in stalled within the cavity 66 by aligning the armature 102, the coil 100 and the magnet core 166 so that the coil is received in a socket in the front surface 98, the opening 186 permits the bearing 190 to be received within the space between the walls 182 and 184 on the armature 102 and the ears 210 on the member 200 are aligned so that the notches 216 receive the projections 160 and the rounded edges 162 permit easy passage of the ears 210 to a position wherein the abutment surfaces 158 on the slider 138 are pressed against the surfaces 214 so that the springs will urge the upper Wall 204 of the magnet core 166 into a firm engagement with the top wall 110 of the housing 30. It will be seen that the projections on the slider cause the abutment surface 158 to be spaced from the top wall 110 a distance less than the thickness of the ears 210. Thus when the magnet core 166 is inserted into the cavity 66, the rounded edge 162 will cause the slider 138 to move away from the top wall 110 so that the ears 210 may be readily positioned between the slider 138 and the top wall 110. The rear surface 164 of the cover 32 has a pair of spring biased supports 167 and 169 secured thereto which are arranged to receive the ears 210 on the member 198 when the cover 32 is secured to the housing 30 in the same manner as the ears 210 on the member 200 were received by the spring biased supports 132 and 134 when the electromagnet 68 was installed in the cavity 66. Thus after the cover 32 is secured to the housing 30, the spring biased supports 132, 34, 167 and 169 will resiliently positlon the magnet core 166 in the cavity 66 so that the rear surface 204 is tightly held against the top wall 110 to provide an efiicient heat conducting path between the magnet core 166 and the material of the housing 30.

The operation of the switching device 20 is as follows. While the switch 20 will operate when mounted on a horizontal support, it is particularly suited to be mounted on a vertical panel, not shown, so that the armature 102 will be moved by the combined forces furnished by gravity and the springs 220 to a position Whereat the pole faces 194 of the armature 102 are separated from the pole faces 206 of the magnet core 166. The energization of the coil 100 through suitable wires connected to terminals 224 causes a mutual magnetic attraction to be generated between the armature 102 and the magnet core 166. The armature 102 is connected to the rotatable bell crank lever 70. The magnet core 166 is resiliently maintained in engagement with the top wall 110 by the spring biased supports 132, 134, 167 and 169 that are respectively carried by the housing 30 and the cover 32. It is well known that the magnet attraction between the armature 102 and the magnet core 166 increases exponentially with the decrease in the distance between the pole faces of the armature 102 and the magnet core 166 and that the magnet attraction increases to a maximum when the pole faces engage each other. The magnetic attraction between the armature 102 and the magnet core 166 causes the armature 102 to move upwardly toward the magnet core 166 and the bell crank lever 70 to rotate about its pivot. The rotating bell crank lever 70 causes the movable contact carrier 74 to move toward the plate 22 to a position wherein the movable contacts 96 engage the contact surfaces 64. The initial movement of the contact carrier 74 is opposed by the force of gravity on the armature 102 and by the springs 220. The subsequent movement of the contact carrier 74 which occurs after the movable contacts 96 engage the contact surfaces 64, is opposed by the force of gravity on the armature 102 and the springs 220 as well as the springs 222 which are associated with the movable contact member 96. Thus the resistance to the movement of the armature 102 toward the magnet core 166 progressively increases as the springs 220 are compressed and markedly increases as the force required to compress the springs 222 is added to the force required to compress the springs 220. The magnet core 166 is exclusively supported in the cavity 66 by the spring biased supports 132, 134, 167 and 169 to have its upper wall 204 tightly pressed against the top wall 110 when the springs 220 and 222 are fully compressed. Thus the heat generated within the electromagnet 68 when the coil 100 is energized will be readily transmitted to the metal housing 30 so the metal housing may serve as a heat sink and dissipate the heat energy generated within the electromagnet 68. However, the springs 140 biasing the supports 132, 134, 167 and 169 are selected to provide a force which will permit the magnet core 166 to move in the direction of the armature 102 in response to the mutual flux between the armature 102 and the magnet core 166 just prior to the engagement between the pole faces 206 on the magnet core 166 and the pole faces 194 on the armature 102. Thus at the instant of impact, the armature 102 and the magnet core 166 will be moving in opposite directions With the magnet core 166 reversing its direction of movement and moving with the armature 102 after the impact has occurred between the armature 102 and the magnet core 166. While the causes therefor are not completely understood, it has been found that resiliently supporting rather than rigidly supporting the magnet core 166 on the housing 30 reduces the noise generated and the shock imparted to the housing .30 which accompanies the impact between the armature 102 and the magnet core 166. Further, it has been found that the resilient support for the magnet core 166 reduces the shock imparted to the housing 30 when the electromagnet 68 is de-energized and the armature 102 is returned to its dropped-out position by the combined force provided by gravity and the springs 220, as well as the springs 222. Further, as disclosed in the Gribble et al. Pat. No. 3,354,- 415, supra, and in patent application Ser. No. 844,151, supra, the movable contact 96 and its supporting structure provides an arrangement which will considerably reduce the bounce which accompanies the engagement between the movable contacts 96 and the stationary contact members 60.

While certain preferred embodiments of the invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpretation within the terms of the following claims.

What is claimed is:

1. In an electromagnetically operated switch, the combination comprising: a housing including at least one metal part having a high coefficient of thermal conductivity providing at least a portion of the external walls of the housing and at least one side wall of an internal cavity within the housing, an armature guided for movement along an axis perpendicular to the side wall between two positions in the cavity, said armature having a pair of pole faces facing the side wall, yieldable means providing a force for constantly urging the armature along the axis in a direction away from the side wall to a first of the said two positions in the cavity, and means including a magnet coil and a magnet core positioned in the cavity to magnetically attract the armature with a force exceeding the force provided by the yieldable means when the coil is energized to thereby cause the armature to move from the first position to a second of the two positions, said core having a pair of pole faces confronting the pole faces of the armature so as to be engaged by the pole faces on the armature when the armature is at the second position and a portion presenting a surface that confronts the side Wall, and means including a plurality of spring biased supports for resiliently positioning the core within the cavity with a force greater than the force provided by the yieldable means so that the confronting surface on the core engages the side wall to provide a heat conducting path for the heat generated within the core by the energized coil when the pole faces of the armature and the core are engaging each other and the armature is at the second position and a force which will permit the core to move toward the armature during the movement of the armature from the first to the second position to reduce the impact shock when the pole faces of the armature and core initially engage each other.

2. The electromagnetically operated switch in accordance with claim 1 wherein the armature, the magnet coil and the magnet core are positioned within the cavity so that the force of gravity acts on the armature and provides at least a portion of the force which constantly urges the armature toward the first position.

3. The electromagnetically operated switch in accordance with claim 1 wherein the housing includes a rear wall, the metal part has an open front wall that provides an entry into the cavity and a cover for the open front wall closes the entry into the cavity and the resilient supports for the magnet core include a pair of supports that are carried by the cover and a pair of supports that are carried by the rear wall.

4. The electromagnetically operated switch in accordance with claim 2 wherein the armature is connected to a movable contact carrier through a bell crank lever and springs reacting on the movable contact carrier provide a portion of the force which constantly urges the armature toward the first position.

'5. The electromagnetically operated switch in accordance with claim 4 wherein the movable contact carrier provides a support for movable contacts and contact springs which are compressed when the armature is at the second position and the supports which position the core within the cavity exert a force greater than the combined forces provided by the yieldable means including the force supplied by the contact springs when the armature is at the second position.

6. The electromagnetically operated switch in accordance with claim 3 wherein the magnet core includes a pair of side plates that are secured on opposite sides of the core with each of the side plates providing a pair of cars that are engaged by the supports that are carried by the cover and the rear wall.

7. The electromagnetically operated switch in accordance with claim 6 wherein each of the cars has a notch therein and each of the supports includes a projection that extends into the notch in the ear which is engaged by the support from which the projection extends.

8. The electromagnetically operated switch in accordance with claim 7 wherein each of the supports includes a surface that engages the ears on the magnet core and the projection extends from the support surface to space the support surface from the side Wall of the cavity.

9. The electromagnetically operated switch in accordance with claim 1 wherein the magnet core is E-shaped and the armature is T-shaped.

10. The electromagnetically operated switch in accordance with claim 4 wherein the connection between the armature and the bell crank is provided by a member having arms secured to the outer sides of the armature and a central portion having an opening therein receiving a bearing member that is rotatable on an arm of the bell crank.

References Cited HAROLD BROOME, Primary Examiner 2 3 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,553,614 Dated January 5, 1971 Inventofl Harald E, whitin and Merlin v Tut-11111111 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

001. 6, line 25, for'"84 4,100' read 844,1 48.

Signed and sealed this 15th day of May 1971.

' (SEAL) Attest:

EDWARD M.FLETGHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

